US3059614A - Device for developing a latent electrostatic image - Google Patents

Description

Oct. 23, 1962 w. LIMBERGER 3,059,514

DEVICE FOR DEVELOPING A LATENT ELEcTRosTATIc IMAGE lll/177 /NVENTO P:

WALTER LmEReER By @m AGEA/T United States VPatent O f 3,059,614 DEVICE FOR DEVELOPING A LATENT ELECTROSTATIC IMAGE WalterLimberger, Hamburg, Germany, assignor to Lumoprint Zindler K.G., Hamburg, Germany, a company of Germany v l Original application June 27,'1957, Ser. No.v 668,528, now Patent No. 2,972,331, dated Feb. 21,1961, Divided and this application June 24, 1959-, Ser. No. 827,671 Claims priority, application IGermany June 29, 1956 S Claims. '(Cl. 118-637) This application is a division ofmy cio-pending U.S. application Serial No. 668,528,5fled June 27, 1957, and now U.S. Patent No. 2,972,331.`

The invention relates to a ldevice for preparing an irnage on ay xerographic layer support by producing the latent electro-static image by illuminating through an objective or by a contactfmethod and by developing this image, so that the layer Vsupport is guided through a toner, whereupon the pigment particles carried on the latent imagetare fused in.

According to known methods for developing a latent electrostatic image in a xerographic layer, the image is rendered visible with pigment particles. These pigment particles are carried by vvery small glass or qu'artz'spheres or ironflings. The spheres orlings form with the pigment particles lthe vso-called ,toner` which, because of the small size of a carrier of the pigment particles, is vpulverulent. The application iseifected in the known methods and devices by, `distributing the toner on thexerographic layer. v

f This known application procedure'hassubstantial disadvantages, since a uniform, distribution of the toner with a distributing deviceis difficult, even if a very heavy distribution is carried out.

There is also the v.disadvantage that a large amount of the toner is removed from thelayerand must be collected. An additionalvortex formation of the coated powder occurs, so thatv the use of enclosed apparatus is coupled with considerabledisadvantages.\ Apart from the soiling of otherparts of theapparatus, an effective cooling in the directproximity'fofzthe distributing device cannot be carried out, since a'cooling-air supply Iadversely affects the distribution on the Xerographic layer. Consequently, the known devices must be constructed relatively large by dividingthe apparatus into several sections, whereby furtherdifiiculties arise in the transport of the layer support. Moreover, the toner needs to be rapidly distributed on the xerographic layer and requires to be shaken ontorthis layer. l,

The invention is.directed'to the problem of avoiding these disadvantages of known methods andA apparatus and of providing .a device which permits the preparation of an image ona xerographic layer support and has extremely small spatial dimensions, so,v that it can be constructed `as a table device. l

This problem ,is` solved in accordance with the invention in that the layer supportrwithv the electrostatic image is not supplied with the toner, but is passedv through an accumulation of the toner. By. this, all .disadvantages which flow from distribution are avoided. and, at the same time, a uniform and thick covering of the electrostatic image with pigment particles is ensured in a particularly advantageous way, without rapid consumption of the toner. y f

The problem ywhich is the basis of the invention is further solved by an apparatus in which guide means for the layer support are provided withinthertone." accumulation in the receptacle containing an accumulation of the toner.

These guide means comprise rotating parts. for exam- Patented Oct. 23, 1962 ple, guide rollers that are arranged as the guide means in the toner accumulation.

In a particularly preferred embodiment, stirring devices tare provided in the toner collected in the container, which have the form for example of paddle wheels or stirring rollers. The direction of rotation of several stirring devices arranged successively in the direction of advance of the layer support may be the same. Preferably, the direction of rotation is so chosen that the sides of the stirrer devices facing the layer support move parallel to the direction of advance.

Within the scope of the invention is an embodiment in which a contrary direction of rotation of the separate stirrer devices is chosen. The purpose of the stirrer devices is to provide agitation of the toner on the side of the layer support provided with the xerographic layer, so that new particles of the toner are continually directed onto the Xerographic layer. The stirring can be used,

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by means of a corresponding arrangement of the stirring devices or also by a corresponding positioning of the blades arranged on the stirrer rollers, at the same time, to effect removal of the consumed toner and a corresponding supply of new toner. Precautions are taken, for example, by suitable guides, so that the consumed toner is moved to the part of the container which is at the back of the layer support.

The construction according to the invention provides an apparatus in which the section of the apparatus receiving the container for the toner can be enclosed With respect to other sections of the container by an intermediate Wall, which is interrupted only by slots for the passage of the layer support. In a preferred embodiment of the invention, the container receiving the toner is arranged in the lower part of the apparatus. Directly above the intermediate Wall enclosing this lower part there is located the illuminating device, in front of which, with reference to the direction of advance of the layer support, a forming or developing device is arranged. Preferably, the forming device and the drive motor for the moving parts are arranged within a housing chamber which is tightly sealed.

Above the container for the toner, on the side at which the layer support is withdrawn from the toner container, there is located a chamber for a brush and/or a disc and/or a nozzle for cleaning the back of the layer support.

A particularly advantageous construction of the apparatus is given in that the xerographic layer support is guided from a supply roll vertically downwards into the toner container in which it runs horizontally. The layer support is drawn vertically upwards from the toner container and, after passing through the heating device, is wound onto a receiving roll.

Further advantages and features of the invention will appear from the following description of the embodiment illustrated in the drawing. In the drawing:

FIG. 1 shows a vertical section through a device according to the invention; and

FIG. 2 shows a section through the device of FIG. 1 on the line II-IL The device illustrated in the drawing consists essentially of anupper part 24 and alower part 25 which are separated from one another by anintermediate wall 26. The intermediate wall is interrupted only byslots 27 and 28 for the passage of thelayer support 29. Directly adjacent theslot 28 there is located afurther opening 30 which is preferably merely an enlargement of theslot 28 and serves for the removal of pigment particles.

In the lower part 25 acontainer 31 is arranged which is lled with thetoner 32. Conveyingdevices 33 and 34, for example in the form of rotating rollers, are arranged within the toner, around which thelayer support 29 is guided. In a preferred construction, theconveying devices 33, 34 consist ofseveral wheels 35 or 36 spaced over the width of thelayer support 29 onaxles 37 and 38.

The layer support is guided with its back over theconveying devices 33 and 34, so that the xerographic layer 1s not damaged by contact with the conveying devices. Stirringdevices 39, 40, 41 are arranged in thecontainer 31 within the toner in front of the side of the Xerographic layer support 29 with the xerographic layer, which cause a continuous stirring of the toner coming into contact with the Xerographic layer, so that the supply of pigment particles to the xerographic layer is ensured.

In the embodiment illustrated, the stirring devices 39-41 are constructed as stirring rollers whose axes run parallel to theaxles 37 and 38 of the conveying devices. The invention includes embodiments in which the axes of the stirring rollers run at an angle to the direction of advance of thelayer support 29. In special cases, the provision of stirring surfaces on the stirring rollers is preferred in order to augment the agitation of the toner in a predetermined direction. For example, this can be done by arranging that the toner particularly in the middle of thecontainer 31, that is in the region of thestirring devices 40, is directed beneath thelayer support 29 toward the longitudinal walls of thecontainer 31, so that the exertion of pressure in the region of the longitudinal walls by the passage through the toner, which is located above thelayer support 29 in thecontainer 31, is prevented by thegap 42 between thelongitudinal wall 43 of thecontainer 31 and the edge of thelayer support 29.

Above theintermediate Wall 26, the housing is divided by ahorizontal partition 63 and a vertical partition 64 into several chambers, of which one chamber receives thesupply roll 44 with the xerographic-layer support. In a further chamber, thecentral drive motor 45 is arranged by which, for example, by means of belt drives 46, 47, 48, all moving parts of the apparatus are driven. In the chamber receiving thedrive motor 45, the formingdevice 49 for the Xerographic layer is also provided. This forming device consists in the embodiment shown ofseveral electrode wires 50 in front of the xerographic layer and anelectrode plate 51 behind the xerographic layer. In the direction of advance of thelayer support 29, which is indicated by thearrow 52, anilluminating device 53 is located behind the formingdevice 49 which in the embodiment shown consists of a tube in which an objective 54 is provided. T he invention also includes constructions in which, instead of the illuminatingdevice 53 shown, the contact method is used for preparing the latent electrostatic image.

The division of the apparatus into separate chambers and the arrangement of moving parts operating on the xerographic layer is so arranged that the xerographic-layer support is guided with the least possible bending from thesupply roll 44 to theroll 55. In the preferred embodiment, in which thecontainer 31 is arranged in the lower part of the apparatus, thelayer support 29 is drawn vertically downwards from thesupply roll 44 arranged at one side of the apparatus in the upper part thereof by theconveyor rollers 56 and 57 and in this direction is guided without bendingto the conveying device 33 within thecontainer 31. In the container 3l, the layer support runs horizontally' and is turned through 90 at the end of the container and is led vertically upwards into a chamber in which a rotatingbrush 58 is arranged. Above this chamber is located theheating device 59 for fusing the pigment particles into the xerographic layer. In front of theheating device 59, the layer support is again turned through 90 and after it has passed through theheating device 59 is guided downwardly to theroll 55. By this guiding of the layer support there is afforded, with small dimensions of the apparatus, a large travel of the layer support through thetoner 32 located in thecontainer 31 and the possibility is also obtained of guiding the layer support, after the forming of the xerographic layer, merely on its rear side. At the same time, the effect is also obtained that the heating device lies in a chamber at the upper side of the upper part of the apparatus so that the heat developed can readily escape.

Thebrush 58 is constructed in the form of a rollet whose length corresponds to the width of the layer support. Thebrush 58 is arranged adjacent of the back of the layer support, namely at the side which is not provided with the xerographic layer, and serves to loosen pigment particles which adhere to the back of the layer support. These pigment particles are directed by the brush, which has a direction of advance opposed to the direction of advance of the layer support, into anopening 30 through which they fall into thecontainer 31. Thewall 60 of the container provided adjacent thebrush 58 is inclined downwardly, so that it guides the freed pigment particles suspended in the brush chamber to theopening 30 as -they sink. The width of the chamber receiving the brush corresponds exactly to the width of thelayer support 29 so that the pigment particles freed from the back of the layer support cannot pass to the front of the layer support. For example, on the side walls of the brush chamber, guides or guide rods are -arranged which cover the slots between the side wall and the edge of thelayer support 29.

Theheating device 59 can be constructed as an infrared radiator or, as shown in the embodiment illustrated, as a resistance heater, which is arranged in front of the xerographic layer. The rollers guiding thelayer support 29 in front of theheating device 59 are indicated at 61 and 62.

Preferably, the chamber receiving thesupply roll 44 is open, so that the particular amount supplied can be observed. All other chambers of the apparatus are enclosed, the walls being merely provided with the requisite slots for the passage of the layer support. The belt drives 46-48 preferably run outside the chambers described and are enclosed in covers.

What I claim is:

1. A device for developing, by contact with a granular toner, a latent electrostatic image on a exible carrier having a xerographic layer, comprising feeder means for said carrier, a receptacle below said feeder means adapted to be tilled to a predetermined level with said toner, guide means within said receptacle forming a path for said carrier, take-up means for said carrier positioned above said receptacle, said path haivng a descending branch extending from said feeder means to said guide means, a substantially horizontal branch extending through an accumulation of said toner below said level, and an ascending branch extending from said guide means to said take-up means, forming and exposure means for said xerographic layer adjacent said descending branch heating means adjacent said ascending branch for fusing adhering toner particles to said carrier, and agitating means positioned adjacent said ascendingbranch for removing loosely adhering toner particles from said carrier and means for returning removed particles to said receptacle.

2. A device for developing, by contact with a granular toner, a latent electrostatic image on a flexible carrier strip having a xerographic layer, comprising a housing; substantially horizontal partition means dividing said housing into a lower and an upper compartment, said partition means being provided with two parallel slots; an upwardly open receptacle in saidlower compartment overlain by said partition means and adapted to be filled to a predetermined level with said toner; first and second roller means in said receptacle rotatable about parallel axes and positioned in substantially vertical peripheral alignment with said slots, respectively, said roller means being disposed at substantially the same height and lying each at least partially below said level; supply means for said carrier strip in said upper compartment; third roller means positioned in said upper compartment between said supply means and said partition means in substantially vertical peripheral alignment with said first roller means and with one of said slots, thereby defining a substantially vertical descending path for said carrier through said one of said slots, said first and second roller means defining a substantially horizontal path for said carrier strip through said toner; forming and exposure means for said xerographic layer in said upper compartment adjacent said descending path; take-up means for said carrier strip in said upper compartment; fourth roller means positioned in said upper compartment between said take-up means and said partition means in substantially vertical peripheral alignment with said second roller means and with the other of said slots, thereby defining a substantially vertical ascending path for said carrier through said other of said slots; and drive means for actuating said take-up means.

3. A device for developing, by contact with a granular toner, a latent electrostatic image on a flexible carrier strip having a xerographic layer, comprising a housing; substantially horizontal partition means dividing said housing into a lower and an upper compartment, said partition means being provided with two parallel slots; an upwardly open receptacle in said lower compartment overlain by said partition means and adapted to be filled to a predetermined level with said toner; first and second roller means in said receptacle rotatable about parallel axes and positioned in substantially vertical peripheral alignment with said slots, respectively, said roller means being disposed at substantially the same height and lying each at least partially below said level; supply means for said carrier strip in said upper compartment; third roller means positioned in said upper compartment between said supply means and said partition means in substantially vertical peripheral alignment with said first roller means and with one of said slots, thereby defining a substantially vertical descending path for said carrier through said one of said slots, said first and second roller means defining a substantially horizontal path for said carrier strip through said toner; forming and exposure means for said Xerographic layer in said upper compartment adjacent said descending path in facing relationship with one side of said carrier strip; take-up means for said carrier strip in said upper compartment; fourth roller means positioned in said upper compartment between said take-up means and said partition means in substantially vertical peripheral alignment with said second roller means and with the other of said slots, thereby defining a substantially vertical ascending path for said carrier through said other of said slots, rotating brush means in said upper compartment positioned adjacent said ascending path along the other side of said carrier strip for removing adherent particles therefrom; drive means for actuating said take-up means; and substantially vertical partition means in said upper compartment separating said brush means from said forming and exposure means.

4. A device for developing, by contact with a granular toner, a latent electrostatic image on a flexible carrier strip having a xerographic layer, comprising a housing: substantially horizontal lower and upper partition means dividing said housing into a lower, and intermediate and an upper compartment, said partition means being each provided with a pair of parallel slots; an unwardly open receptacle in said lower compartment overlain by said lower partition means and adapted to be filled to a predetermined level with said toner; first and second roller means in said receptacle rotatable about parallel axes and positioned in substantially vertical peripheral alignment with said slots, respectively, said roller means being disposed at substantially the same height and lying each at least partially below said level; supply means for said carrier strip in said housing above said lower partition means; third roller means positioned in said upper compartment between said supply means and said partition means in substantially vertical peripheral alignment with said first roller means and with one of said slots of each pair, thereby defining a substantially vertical decending path for said carried through said one of said slots, said first and second roller means defining a substantially horizontal path for said carrier strip through said toner; forming and exposure means for said Xerographic layer in said intermediate compartment adjacent said descending path in facing relationship with one side of said carrier strip; take-up means for said carrier strip in said housing above said lower partition means; fourth roller means positioned in said upper compartment between said take-up means and said partition means in substantially vertical peripheral alignment with said second roller means and with the other of said slots of each pair, thereby defining a substantially vertical ascending path for said carrier through said other of said slots; rotating brush means in said intermediate compartment positioned adjacent said ascending path along the other side of said carrier strip for removing adherent particles therefrom; drive means for actuating said takeup means; heating means in said upper compartment above said brush means for fixing a xerographic image on said layer; and substantially vertical partition means in said housing in at least said intermediate compartment separating said brush means from said forming and exposure means.

5. A device for developing, by contact with a granular toner, a latent electrostatic image on a flexible carrier strip having a Xerographic layer, comprising a housing; substantially horizontal partition means dividing said housing into a lower and an upper compartment, said partition means being provided with two parallel slots; an upwardly open receptacle in said lower compartment overlain by said partition means and adapted to be filled to a predetermined level with said toner; first and second roller means in said receptacle rotatable about parallel axes and positioned in substantially vertical peripheral alignment with said slots, respectively, said roller means being disposed at substantially the same height and lying each at least partially below said level; means including a supply reel for said carrier strip positioned in said upper compartment and defining a substantially vertical descending path for said carrier through one of said slots, said first and second roller means defining a substantially horizontal path for said carrier strip through said toner; forming and exposure means for said xerographic layer in said upper compartment adjacent said descending path; means including a take-up reel for said carrier strip positioned in said upper compartment and defining a substantially vertical ascending path for said carrier through the other of said slots; heating means in said upper compartment adjacent said ascending path between said takeup reel and said partition means for fusing adhering toner particles to said carrier; and drive means for rotating said take-up reel.

References Cited in the file of this patent UNITED STATES PATENTS 2,221,776 Carlson Nov. 19, 1940 2,338,266 Skoning Ian. 4, 1944 2,340,897 Pierson Feb. 8, 1944 2,348,166 Cavanaugh et al May 2, 1944 2,676,899 Hackley Apr. 27, 1954 2,761,416 Carlson Sept. 4, 1956 2,826,168 Grant Mar. ll, 1958 2,832,511 Stockdale et al Apr. 29, 1958 2,851,373 Tregay et al Sept. 9, 1958 2,919,672 Benn et al. Jan. 5, 1960

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